Effect of calcium and magnesium ions in microbial cells adhesion of attached growth systems for the enhancement of biohydrogen production

Abstract

This study is aim to enhance the hydrogen production performance by addition of calcium and magnesium ions in attached growth systems to reduce electrostatic repulsion between negatively charged bacteria by introducing the multi-valence positive ion (calcium and magnesium) into the seed sludge. The effect of calcium and magnesium ions on thermophilic biohydrogen production by a mixed culture, obtained from palm oil mill effluent and granular activated carbon (GAC) as the support material were used in this study. The batch experiments were carried out 60oC by feeding the anaerobic sludge bacteria with sucrose-containing synthetic medium at an initial pH of 5.5 under anaerobic conditions. The repeated batch cultivation process was conducted by adding different concentration of calcium and magnesium at range 0.25g/L to 1.0g/L and 0.025g/L to 0.15g/L. Observations using scanning electron microscopy (SEM) illustrated the attachment of rod-shaped bacterial cells on the GAC at 60oC. The results showed that the calcium and magnesium will enhance the fermentative hydrogen production under thermophilic conditions.